The present invention relates to a video zooming method and a video camera adopting the same, and more particularly, to a video zooming method and a video camera adopting the same, in which although an auto-focusing is performed at a high-power magnification when a zooming operation is performed using a zoom lens, a near object is prevented from becoming out of focus.
Video cameras which have recently become popular for general home use employ a zoom lens having a range of magnifications of 2-10. A zoom lens can sequentially vary a focal distance of the lens from a wide-angle to a telephoto range, by a process which is called zooming. The zoom lens can vary the size of an image at random without departing from a focus if an object is in focus and then zoomed. A video camera also uses an auto-focus zoom lens. An auto-focus (AF) zoom lens adopts a fundamental principle which can automatically focus a camera on an object when the camera is directed toward the object. An AF mechanism of a video camera is disclosed in detail in an article xe2x80x9cAuto Function (AF, AE, AWB)xe2x80x9d, published in Television Institute Journal, Vol. 49, No. 2, pp. 145-149, 1995. A conventional zooming method for a video camera employing an auto-focus zoom lens is schematically shown in FIG. 1.
FIG. 1 is a flow-chart diagram for explaining a conventional zooming method for a video camera.
In FIG. 1, a user can vary a magnifying power of a lens into a wide-angle state or a tele-state via a telephoto/wide-angle (T/W) switch which is attached to the video camera. When a wide-angle state is selected in the T/W switch, a scene appears farther and farther away, while when a tele-state is selected, the scene appears closer and closer. When the focus is adjusted in a video camera, an object is first brought into focus at the state where a zoom-in operation is not performed and then a zoom-out operation is performed; the object may be out of focus. Thus, when adjusting a focus, it is judged in step 101 whether a user of a video camera selects a magnification of the lens as a tele-state via a T/W switch. If the magnification of the lens selected is a tele-state, the video camera drives a zoom motor and performs a zooming operation in which the zoom lens is zoomed in a zoom-in direction (step 102). Since the position of a focus lens varies when zooming, the video camera drives an AF motor and automatically adjusts the focus lens, to thereby accurately focus on the object at the current zooming state (step 103).
However, when zooming at a high-power magnification, auto-focusing may cause a focal point of an object to be out of focus since the position of the focus lens varies. Such a problem cannot be solved in the case of a recent video camera which can perform a high-power magnification up to twenty magnifications via a digital zoom function.
To solve the above problems, it is an object of the present invention to provide a video camera zooming method for performing a digital zooming operation based on information on the nearest positions of a zoom lens and a focus lens which do not cause an object to be out of focus at the state of a high-power magnification of the zoom lens.
It is another object of the present invention to provide a video camera adopting the above zooming method.
To accomplish the above object of the present invention, there is provided a video camera zooming method comprising the steps of: (a) judging whether a focus lens is in focus while performing an optical zoom-in operation; (b) storing zoom lens position information and focus lens position information whenever it is determined that the focus lens is in focus in step (a); (c) performing an optical zooming operation and a focusing operation using the focus lens position information and corresponding zoom lens position information which are stored in step (b) when the focus lens is not in focus in step (a); and (d) performing a digital zooming operation with respect to a video signal obtained in step (c).
There is also provided a video camera comprising: a lens unit having a zoom lens and a focus lens; a memory; a control unit for controlling the lens unit based on an edge component so that an optical zoom-in operation and a focusing operation are performed, storing focus lens position information and corresponding zoom lens position information in the memory whenever the lens unit is in focus, and controlling the lens unit according to the focus lens position information and the corresponding zoom lens position information stored in the memory when the lens unit is out of focus; and a signal processor for detecting an edge component from a video signal received via the lens unit, supplying the detected edge component to the control unit and performing a digital zooming operation with respect to the video signal received when the lens unit is controlled based on the focus lens position information and the zoom lens position information stored in the memory.